[petsc-users] RCM for ILU?

[Jed Brown]

Qin Lu <lu_qin_2000 at yahoo.com> writes:

> Hello,
>  
> Is the RCM reordering available for ILU preconditioner in PETSc? The manual says RCM works with LU factorization, but it does not mention it for preconditioners. 

It works for all factorization preconditioners (ILU, ICC, LU, Cholesky).

~/petsc/src/ksp/ksp/examples/tutorials$ ./ex2 -m 100 -n 100 -ksp_view -pc_type ilu -pc_factor_mat_ordering_type rcm
KSP Object: 1 MPI processes
  type: gmres
    GMRES: restart=30, using Classical (unmodified) Gram-Schmidt Orthogonalization with no iterative refinement
    GMRES: happy breakdown tolerance 1e-30
  maximum iterations=10000, initial guess is zero
  tolerances:  relative=9.80296e-07, absolute=1e-50, divergence=10000
  left preconditioning
  using PRECONDITIONED norm type for convergence test
PC Object: 1 MPI processes
  type: ilu
    ILU: out-of-place factorization
    0 levels of fill
    tolerance for zero pivot 2.22045e-14
    using diagonal shift on blocks to prevent zero pivot [INBLOCKS]
    matrix ordering: rcm
    factor fill ratio given 1, needed 1
      Factored matrix follows:
        Mat Object:         1 MPI processes
          type: seqaij
          rows=10000, cols=10000
          package used to perform factorization: petsc
          total: nonzeros=49600, allocated nonzeros=49600
          total number of mallocs used during MatSetValues calls =0
            not using I-node routines
  linear system matrix = precond matrix:
  Mat Object:   1 MPI processes
    type: seqaij
    rows=10000, cols=10000
    total: nonzeros=49600, allocated nonzeros=50000
    total number of mallocs used during MatSetValues calls =0
      not using I-node routines
Norm of error 0.00314611 iterations 84
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